Photosensitive semiconductor device

ABSTRACT

An object of the present invention is to prevent deterioration of adhesion between a molding resin and lead frame and a light transmission characteristic due to the attachment of a translucent resin to an upper surface of the lead frame upon charging a photocoupler with the translucent resin. 
     A concave portion is defined in an island of a lead frame to which a photosensitive semiconductor device is fixed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a photosensitive semiconductor device, andparticularly to a photocoupler having a photo-emitting device and aphoto-detecting device shaped in integral form.

2. Description of the Related Art

FIG. 4 is a view showing a section structure of a previously-usedphotocoupler. The prior art photocoupler will be explained below withreference to FIG. 4.

In FIG. 4, reference numerals 1 and 2 indicate a lead frame on thephoto- or light-emission side and a lead frame on the photo- orlight-reception side, respectively. A light- or photo-emitting device 3and a light- or photo-receiving or -detecting device 4 are fixed toislands of the lead frames 1 and 2 respectively. Designated at numeral 5shown in FIG. 4 is a light-transmissive or translucent resin, whichcouples the photo-emitting device 3 and the photo-detecting device 4 toeach other in an opposed state. Further, they are resin-sealed with anepoxy molding resin to prevent external random light.

FIGS. 5(A) and 5(B) are respectively views showing configurations ofconventional lead frame 1 on the light-emission side and lead frame 2 onthe light-reception side. FIG. 6 is a view illustrating the manner ofcharging of the translucent resin 5. A method of manufacturing thephotocoupler shown in FIG. 4 will be explained below with reference toFIGS. 5 and 6.

A photo-emitting device 3 and a photo-detecting device 4 are fixed todiagonally-shaded regions of islands of the lead frames shown in FIGS.5(A) and 5(B).

Thereafter, the lead frame 1 with the photo-emitting device 3 placedthereon and the lead frame 2 with the photo-detecting device 4 placedthereon are placed as opposed to each other as shown in FIG. 6. In thiscondition, the translucent resin 5 is filled between the lead frame 1and the lead frame 2 from diagonally above the lead frame 1 by the useof a dispenser 7 to thereby couple the photo-emitting device 3 and thephoto-detecting device 4 to each other.

Thereafter, the whole part is plastic-sealed with a mold sealingmaterial 6 to create the photocoupler shown in FIG. 4.

However, the conventional photocoupler has a problem in that uponfabrication of the photocoupler, the translucent resin 5 to be filledadheres to an upper surface (corresponding to a surface not opposed tothe lead frame 2 on the light-emission side) of the lead frame 1 due toa subtle position displacement of the dispenser 7 for filling thetranslucent resin 5 (this state is indicated by a circle mark in FIG.6).

As a result, the shape of the translucent resin 5 varies according tothe position of the dispenser 7. This type of photocoupler has a problemin that since light reflected from an interface between the translucentresin 5 and the molding resin 6 is detected by the photo-detectingdevice 4, the efficiency of light transmission by the photocouplervaries as the translucent resin 5 changes in shape.

Further, a problem also arises in that the adhesion between the leadframe 1 and the molding resin 6 is deteriorated due to the attachment ofthe translucent resin 5 to the upper surface of the lead frame 1.

SUMMARY OF THE INVENTION

With the foregoing problems in view, it is therefore an object of thepresent invention to prevent deterioration of adhesion between a moldingresin and a lead frame and a light transmission characteristic due tothe adhesion of a translucent resin to an upper surface of the leadframe upon charging a photocoupler with the translucent resin.

According to one aspect of this invention, for achieving the aboveobject, there is provided a photosensitive semiconductor devicecomprising a first lead frame having a first island to which aphoto-emitting semiconductor device is fixed, a second lead frame havinga second island to which photo-detecting semiconductor device is fixed,a translucent resin for coupling the photo-emitting semiconductor deviceand the photo-detecting semiconductor device to each other in an opposedstate, a sealing material for surrounding the translucent resin, and aconcave portion defined in either one of ends of the first and secondislands.

Typical ones of various inventions of the present application have beenshown in brief. However, the various inventions of the presentapplication and specific configurations of these inventions will beunderstood from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as theinvention, it is believed that the invention, the objects and featuresof the invention and further objects, features and advantages thereofwill be better understood from the following description taken inconnection with the accompanying drawings in which:

FIG. 1 is a view showing a lead frame on the light-emission side, whichis employed in a first embodiment of the present invention;

FIG. 2(A) is a view illustrating the manner in which a translucent resinis charged into a photocoupler according to the present invention;

FIG. 2(B) is a view illustrating an alternative manner in which atranslucent resin is charged into a photocoupler according the presentinvention;

FIG. 3 is a view depicting a lead frame on the light-emission side,which is employed in a second embodiment of the present invention;

FIG. 4 is a view showing a section structure of a conventionalphotocoupler;

FIG. 5 is a view illustrating a lead frame of a conventionalphotocoupler; and

FIG. 6 is a view depicting the manner in which a translucent resin ischarged into a conventional photocoupler.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will hereinafter bedescribed in detail with reference to the accompanying drawings.

[First Embodiment]

FIG. 1 is a view showing a lead frame on the light-emission side, of aphotocoupler according to a first embodiment of the present invention.FIG. 2 is a view illustrating the manner in which a light-transmissiveor translucent resin is charged into the photocoupler according to thepresent invention in a state in which a photo-emitting device and aphoto-detecting device are opposed to each other. In these drawings,components common to those shown in FIGS. 4, 5 and 6 are identified bythe same reference numerals. The present invention will be explainedbelow with reference to FIGS. 1 and 2.

A lead frame 10 on the light-emission side has an island 102 with aphoto-emitting device placed thereon, and leads 103 and 104 electricallyconnected to the outside. As shown in FIG. 1, the island 102 with thephoto-emitting device mounted thereon has a concave portion 110 whosewidth X is about 0.3 mm, and sharp edges (convex portions) 111, whichare respectively provided in the neighborhood of the center of an endthereof and at both ends thereof. It is desirable that the width X ofthe concave portion 110 is slightly greater than the diameter of adispenser 7 for filling a translucent resin 5.

On the other hand, a lead frame on the light-reception side is similarto the conventional one shown in FIG. 5(B).

A method of manufacturing a photocoupler according to the presentinvention will be described below.

In the lead frame 10 on the light-emission side, a photo-emitting device3 is fixed to a diagonally-shaded region in FIG. 1. A photo-detectingdevice is similar to that employed in the prior art.

Thereafter, the lead frame 10 with the photo-emitting device 3 fixedthereto and the lead frame 2 with the photo-detecting device 4 fixedthereto are placed as opposed to each other as shown in FIG. 2. In thiscondition, the translucent resin 5 is charged between the lead frame 10and the lead frame 2 from diagonally above the lead frame 10 by the useof the dispenser 7 to thereby couple the photo-emitting device 3 and thephoto-detecting device 4 to each other.

Thereafter, the whole part is resin-sealed with a mold sealing material6 to process the lead frames into final shapes, thereby creating aphotocoupler according to the present invention.

According to the present invention, even if the dispenser for fillingthe translucent resin 5 is subtly shifted in position due to thedefinition of the concave portion 110 in the island 102 of the leadframe 10 in the process for fabricating the photocoupler, thetranslucent resin 5 flows into the lower surface of the lead frame 10through the concave portion 110. Therefore, no translucent resin 5adheres to the upper surface of the lead frame 10. Thus, the adhesion ofthe lead frame 10 to the mold sealing material 6 is improved.

Since the edges (convex portions) 111 exist in the island 102 of thelead frame 10, the translucent resin 5 can be shaped to the leadingportions or tips of the sharp edges (convex portions) 111 under theaction of the surface tension of the translucent resin 5. Namely, thetranslucent resin 5 can be shaped into an offset-free stable form owingto the existence of the sharp edges (convex portions) in the island.Further, a light transmission characteristic can be also stabilized.

[Second Embodiment]

FIG. 3 is a view showing a lead frame 20 on the light-emission side,which is employed in a second embodiment of the present invention. Inthe second embodiment, a concave portion 210 defined in an island 202 ofthe lead frame 20 is shaped into an arcuate form. Other elements ofstructure are similar to those employed in the first embodiment.

According to the second embodiment, since the shape of the concaveportion 210 is brought into the circular arc, an advantageous effectsimilar to that obtained in the first embodiment is obtained. Inaddition to this effect, the surface tension of the translucent resin 5increases upon charging the translucent resin 5 between the framesbecause portions orthogonal to the concave portion 210 do not exist,whereby the translucent resin 5 having a stabler shape can be formed. Inother words, the efficiency of light transmission can be obtainedstabler.

The present invention is not necessarily limited to the concave portionshaving the shapes illustrated in the first and second embodiments. Otherconcave shapes may be used if those having effects similar to the aboveare taken.

Although the first and second embodiments have described the case inwhich the translucent resin is filled from the light-emission side, thetranslucent resin may be charged from the light-reception side. Anexample of such filling from the light reception side is shown in FIG.2(B), in which the concave portion 110 is now in the lead frame 2 of thephoto-detecting device 4.

While the present invention has been described with reference to theillustrative embodiments, this description is not intended to beconstrued in a limiting sense. Various modifications of the illustrativeembodiments, as well as other embodiments of the invention, will beapparent to those skilled in the art on reference to this description.It is therefore contemplated that the appended claims will cover anysuch modifications or embodiments as fall within the true scope of theinvention.

What is claimed is:
 1. A photosensitive semiconductor devicecomprising:a first lead frame having a first extension to which aphoto-emitting semiconductor device is fixed; a second lead frame havinga second extension to which a photo-detecting semiconductor device isfixed; a translucent resin for coupling said photo-emittingsemiconductor device and said photo-detecting semiconductor device toeach other in an opposed state; a sealing material for surrounding saidtranslucent resin; and a concave portion defined in an end of one ofsaid first and second extensions that is in whichever is smaller, saidphoto-emitting device or said photo-detecting device.
 2. Aphotosensitive semiconductor device according to claim 1, wherein saidconcave portion is shaped into a circular arc form.
 3. A photosensitivesemiconductor device according to claim 1, wherein a width of saidconcave portion is greater than a diameter of a dispenser for fillingsaid translucent resin.
 4. A photosensitive semiconductor deviceaccording to claim 1, wherein said concave portion is in said firstextension.